Embryonic Development in Man. 3G3 



least donbtfnl whether we will ever have such a specimen at our 

 disposal.'' 



Jung then points out the great rarity of young human ova ob- 

 tained in sliii. He mentions those of Peters, von Spec, Leopold, van 

 Heukelom and Frassi-Keibel, and he finds objectionable features 

 in all of them. 



The youngest and undoubtedly most valuable of these specimens 

 is that of Peters. Without trying to detract from the great value 

 and fundamental importance of the Peters' specimen, it is proper 

 to point out that it came from a case which strongly suggests the 

 probability of pathologic changes.^ Peter's ovum was obtained 

 from a woman who committed suicide by swallowing a large quan- 

 tity of caustic i^otash solution, and who died three hours later. 

 Such a rapid death after the ingestion of the fixed mineral alkalies 

 is extremely rare, and must be connected with marked changes of 

 the blood itself and of its circulation. I can find only the very in- 

 complete record of a single similar case, that of a boy, said to have 

 died three hours after swallowing lye. 



. The embryo in Peters' specimen is said to be less well preserved 

 than the chorion. It was described by Count von Spec as show- 

 ing two very small epithelial cavities (the amnion and yolk sac), 

 embedded in the chorionic mesoderm. The connection between the 

 embryo and the chorion was thus so extensive that it was impossible 

 to speak of an isolated body-stalk. Count von Spee was uncertain 

 whether ''the first little milage of an entodermal diverticulum (al- 

 lantoic duct)" was present or not. The amniotic cavity was com- 

 pletely closed. It was lined in part by the very thin amniotic 

 epithelium and in part by the tall columnar cells of the embryonic 

 plate. A thin layer of mesoderm extended between the plate and the 

 yolk sac, crossing the median line except toward one end of the em- 

 bryo (thought to be the cranial end). E'othing is said of a neuren- 

 teric canal, or of blood vessels. Peters estimated the length of the 

 embryo to be 190 microns. 



A reconstruction of Peters' ovum was made by Keibel, from nine- 



'The conditions foiind, wliicli are probalily pathologic, will lie pointed out 

 below. 



